Fig. 7.

Spectroscopic PA imaging of absorbing targets in a turbid medium. (a) Examples of PA images displayed on a log (dB) scale at 3 different wavelengths (715 nm, 795 nm and 875 nm) for Phantom Study II. The first, second and third tubes were filled with GNR solution, water and black ink, respectively. The scattering medium was a solution of intralipid and Prussian blue ink. The pixel value of the image is associated with the PA pressure. Dotted circles in the image indicate tube cross-sections. (b) and (c) columns show parameter estimates using nanoparticle signals in Tube I and black signals in Tube III, respectively, and spectrum correction results using the estimates. First and second rows represent estimates of effective light attenuation and reduced scattering coefficients in a turbid medium, respectively. Points marked ($\text{o})$ and ($⊲$) denote estimates using Model I and Model II, respectively. The dotted line is obtained by smoothing estimates over wavelength. Third and fourth rows show absorption spectra of the nanoparticle and black ink, respectively. Magenta curves with points marked (◇) correspond to measured PA absorption spectra, i.e. without fluence correction. Orange and blue curves with points marked ($\text{o}$) and ($⊲$) respectively correspond to ink and GNR absorption spectra obtained after applying fluence correction using Model I and Model II, respectively. Dotted lines indicate the reference target spectra measured independently with optical spectrophotometry.